Skull morphometry of Pygoscelis (Sphenisciformes): inter and intraspecific variations

Abstract

Morphological diversity of 47 pygoscelid skulls was tested empirically through geometric morphometrics approach. Using 14 landmarks, shape is analyzed independently of other aspects of the body form. The shape disparity within and between the three living species of Pygoscelis is explored as well as how the structure of the skull is related to food preferences. Comparison of the three mean configurations of the species suggests that differences among groups are small relative to the variability within each group. However, some differences at the posterior portion of the braincase are indicated. Sexual dimorphism within each species is not noticeable. Comparison with a piscivorous species (Spheniscus humboldti) shows two cranial patterns: pygoscelid type with wide nasal gland depression limited by well-marked edges, shallow temporal fossae, and a poorly developed temporal nuchal crest; the second type represented by Spheniscus humboldti with laterally open nasal gland depression, deep temporal fossae, and a well-developed temporal nuchal crest.

Appendix: materials used in the morphometric analyses performed

P. adeliae: MLP 32, MLP 33, MLP 415, MLP 416, MLP 417, MLP 418, MLP 419, MLP 420, MLP 421, MLP 422, MLP 423, MLP 424, MLP 425, MLP 426, MLP 427, MLP 428, MLP 429, MLP 430, MLP 431, MLP 432, MLP 433, MLP 434. Pygoscelis antarctica: IAA 54, IAA 65, IAA 76, IAA 157, IAA 158, MLP 435, MLP 436, MLP 437, MLP 438, MLP 439, MLP 440, MLP 441, MLP 442, MLP 443, MLP 444, MLP 447. Pygoscelis papua: IAA 24, IAA 81, IAA 82, IAA 88, IAA 160, MLP 449, MLP 451, MLP 463, MLP 468. Spheniscus humboldti: MLP 686.